Description
Rhombophryne matavy is a very heavy-set, robust frog that has a snout-vent length of 39 - 49 mm in adult males. No females were examined for the species description. The head is wider than long, but narrower than the body. The snout is short and rounded from the dorsal and lateral views. The nostrils are slightly protuberant, located close to the tip of the snout and further from the eyes. They have distinct vomerine teeth that form transverse rows behind the internal nares, beginning close to the jaw. They have easily recognizable canthus rostralis, and the loreal region is concave. The eyes are small. They have two ridges behind their eyes. The tympanum is noticeable but less defined. The fore- and hind limbs are short and robust. They have a large inner metacarpal tubercle but no outer metacarpal tubercles. They have single subarticular tubercles with no webbing between the fingers. Their lateral metatarsalia is connected. They have large inner metatarsal tubercles that are shovel-like, and an indistinct outer metatarsal tubercle. Their fourth toe is the largest followed by their third, fifth, second, and first; their third toe is visibly longer than their fifth. The skin on their dorsal surface is tuberculate, particularly on the flanks, whereas on their venter, chest, and throat, it is relatively smooth. There is also no dorsolateral fold present. The opening of the cloaca faces the posterior end (D’Cruze et al. 2010).

DIAGNOSIS:

The lack of an expanded terminal finger distinguishes Rhombophryne from other cophyline genera, specifically, Anodonthyla, Cophyla, and Platypelis, and several species of Plethodontohyla. Additionally, Rhombophryne is much larger than Madecassophryne and Stumpffia (D’Cruze et al. 2010).

Within the genus, Rhombophryne matavy is similar to R. alluaudi, R. coudreaui, R. coronata, R. guentherpetersi, R. laevipes, R. minuta, R. serratopalpebrosa, R. testudo; however, there are some distinguishable differences that set them apart. In contrast with these other eight species, the focal species has much shorter hind legs as the tibiotarsal articulation does not reaching the insertion of the arms. Additionally, R. matavy has a larger snout-vent length than R. coudreaui, R. coronata, R. guentherpetersi, R. minuta, and R. serratopalpebrosa. Smaller eyes and post-orbital ridges in R. matavy further differentiate the species from R. coronata, R. serratopalpebrosa, R. guentherpetersi, P. alluaudi, P. laevipes, and P. minuta. Furthermore, having less granular skin R. matavy also differs from R. coudreaui. Lastly, this species very closely resembles R. testudo, but the focal species lack barbels on their lower lip, which makes it easier to tell them apart (D’Cruze et al. 2010).

COLORATION:

Living R. matavy have dark marks in the shape of two irregular chevrons interspersed on a brown dorsum. The majority of the head is a dark brown, a deeper shade than the dorsum. The limbs are also a dark brown. The colors of the flank and dorsum do not form a distinct line, with the colors blending together. The first two fingers and the first two toes are yellow with brown spots, while the other digits are brown. The skin surrounding the cloaca is white. Ventral sides of the limbs are a pinkish brown, and the undersides of the thighs also have white spots. The chest is pinkish brown, and the throat is black. Different protuberances range from pinkish brown to greyish white. The irises are mostly black with gold flecks interspersed and are lined with a black border (D’Cruze et al. 2010). In preservative, R. matavy has dark brown coloration on its dorsum. By contrast, the inner two fingers, the inner three toes, and the protuberance on the inside of the metatarsal are white. Similarly, the undersides of the fingers and toes are white. The underside of the frog is dark brown (D’Cruze et al. 2010).

VARIATION:

Individuals within this species vary in dorsal skin texture, with some individuals having coarser skin and more spiny protuberances. Color variation was also observed; golden spotting was present in different areas of the iris and darker colored shapes were present on the dorsums of some individuals. As there were no observations of females taken, sexual dimorphism is not known (D’Cruze et al. 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Madagascar

View distribution map in BerkeleyMapper.

Rhombophryne matavy is thought to be endemic to northern Madagascar, in the Forêt d'Ambre Special Reserve. However, it is possible they may have a wider distribution reaching the lower limits of the Montagne d'Ambre National Park. Its lower elevation limit is 428 meters above-the-sea level and its extent of occurrence is 48 km² (IUCN 2020).

Rhombophryne matavy inhabits lowland transitional rainforest and they do not migrate. The holotype for this species was found underneath the base of a small tree calling from a burrow located beneath leaves; excavation also revealed other individuals in similar locations (D’Cruze et al. 2010).

Life History, Abundance, Activity, and Special Behaviors

Rhombophryne matavy is a fossorial species and is relatively rare, being endemic only to Forêt d'Ambre Special Reserve (D’Cruze et al. 2010).

Though nothing is known about the species’ reproduction, a closely related species, R. testudo, has a reproductive mode involving some parental care for juveniles developing in ground burrows (Kohler et al. 1997). Thus, R. matavy may share a similar reproductive mode. In a similar line of extrapolation from R. testudo, R. matavy may have non-feeding tadpoles (Kohler et al. 1997).

Rhombophryne matavy males emitted soft warm-up notes before vocalizing. The call duration lasts 2091 - 2202 ms and contains five notes per call with a note duration of 161 - 209 ms. Internote intervals last 267 - 353 ms. The notes in this species' call showed different amplitude modulation with the maximum energy at the last note. There is also frequency modulation with a slight sweep and a fast drop in each note. The maximum call frequency was between 1588 - 1688 HZ and the additional harmonic frequencies were at about 880, 2500, 3360, 4160, 5060, and 5840 Hz. The repetition and the strength of the call varies depending on motivation (D’Cruze et al. 2010).

The holotype’s remarkably large feces revealed remains of medium-sized insects such as head capsules and elytra of Coleoptera (D’Cruze et al. 2010).

Trends and Threats
Rhombophryne matavy is currently “Critically Endangered” and experiencing population decline according to the IUCN Red List. They can be found in a protected area known as Forêt d'Ambre Special Reserve (IUCN 2020).

The anuran’s habitat is located close to the capital of Antsiranana province and nearby communes such as Sakaramy and Joffreville; therefore, human activities have a profound impact on the species’ population. Some examples of threats that have negatively impacted R. matavy’s already small forest habitat include, but are not limited to, agriculture clearance for crops, small-scale quarrying, zebu grazing, and production of charcoal and timber (D’Cruze et al. 2010). Energy production, mining, and logging have also been known to contribute to their population decline (IUCN 2020).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Mining

Comments

PHYLOGENETIC RELATIONSHIPS:

The placement of the genus Rhombophryne with regards to the genus Stumpffia is somewhat unclear, however there is evidence that Rhombophryne and Stumpffia are sister taxa based on their genetics, ecology, and morphology (Scherz et al. 2016).

ETYMOLOGY (Origin or explanation of scientific name):

Due to this species’ robust body shape, it was given the species epithet “matavy”, which translates to “fat” in Malagasy (D’Cruze et al. 2010).

As of 2021, R. matavy is listed as Plethodontohyla matavy by IUCN (2020).

References

D’Cruze, N., Kohler, J., Vences, M., Glaw, F. (2010). "A new fat fossorial frog (Microhylidae: Cophylinae: Rhombophryne) from the rainforest of the Foret D’Ambre Special Reserve, northern Madagascar." Herpetologica, 66(2), 182-191. [link]

IUCN SSC Amphibian Specialist Group. (2020). “Plethodontohyla matavy (amended version of 2016 assessment)”. The IUCN Red List of Threatened Species 2020: e.T49581455A177138489. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T49581455A177138489.n. Downloaded on 01 February 2021.

Kohler, J., Glaw, F., Vences, M. (1997). "Notes on the reproduction of Rhombophryne (Anura: Microhylidae) at Nosy Be, northern Madagascar." Revue Française d’Aquariologie et Herpetologie 24:53–54.

Scherz, M. D., M. Vences, A. Rakotoarison, F. Andreone, J. Köhler, F. Glaw, and A. Crottini. (2016). "Reconciling molecular phylogeny, morphological divergence and classification of Madagascan narrow-mouthed frogs (Amphibia: Microhylidae)." Molecular Phylogenetics and Evolution 100: 372–381. [link]

Species Account Citation: AmphibiaWeb 2021 Rhombophryne matavy <https://amphibiaweb.org/species/7497> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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